fix compaction entry read exception

[hangc0276]

Motivation

When read entry from compacted ledger, it will get the following exception when read the end of compacted ledger

12:04:11.193 [broker-topic-workers-OrderedScheduler-7-0] ERROR org.apache.bookkeeper.client.LedgerHandle - IncorrectParameterException on ledgerId:3753 firstEntry:-4276948922 lastEntry:-4276948822
12:04:11.194 [broker-topic-workers-OrderedScheduler-7-0] ERROR org.apache.pulsar.broker.service.persistent.PersistentDispatcherSingleActiveConsumer - [persistent://public/default/__change_events-partition-0 / multiTopicsReader-5358dc9a38-Consumer{subscription=PersistentSubscription{topic=persistent://public/default/__change_events-partition-0, name=multiTopicsReader-5358dc9a38}, consumerId=3, consumerName=fd550, address=/202.168.117.36:45676}] Error reading entries at 3837:0 : java.util.concurrent.CompletionException: org.apache.bookkeeper.client.BKException$BKIncorrectParameterException: Incorrect parameter input - Retrying to read in 15.0 seconds

The reason is when startPoint == NEWER_THAN_COMPACTED it will set cursor to normal ledger to read the following entry and should just complete the read cycle and return.

pulsar/pulsar-broker/src/main/java/org/apache/pulsar/compaction/CompactedTopicImpl.java

Lines 109 to 118 in e9c5476

	if (startPoint == NEWER_THAN_COMPACTED) {
	cursor.seek(compactionHorizon.getNext());
	callback.readEntriesComplete(Collections.emptyList(), ctx);
	}
	return readEntries(context.ledger, startPoint, endPoint)
	.thenAccept((entries) -> {
	Entry lastEntry = entries.get(entries.size() - 1);
	cursor.seek(lastEntry.getPosition().getNext());
	callback.readEntriesComplete(entries, ctx);
	});

Modification

1. When read the end of compacted ledger, just return this read cycle.

[codelipenghui]

The change looks good to me, is it able to add a test for avoiding the regression?